[v4,3/3] kunit: fix bug of extra newline characters in debugfs logs

Fix bug of the extra newline characters in debugfs logs. When a
line is added to debugfs with a newline character at the end,
an extra line appears in the debugfs log.

This is due to a discrepancy between how the lines are printed and how they
are added to the logs. Remove this discrepancy by checking if a newline
character is present before adding a newline character. This should closely
match the printk behavior.

Add kunit_log_newline_test to provide test coverage for this issue.  (Also,
move kunit_log_test above suite definition to remove the unnecessary
declaration prior to the suite definition)

As an example, say we add these two lines to the log:

kunit_log(..., "KTAP version 1\n");
kunit_log(..., "1..1");

The debugfs log before this fix:

 KTAP version 1

 1..1

The debugfs log after this fix:

 KTAP version 1
 1..1

Signed-off-by: Rae Moar <rmoar@google.com>
Reviewed-by: David Gow <davidgow@google.com>
---

Changes from v3 -> v4:
- Slight formatting change in test.h regarding "\" placement.

Changes from v2 -> v3:
- Changes to commit message.

Changes from v1 -> v2:
- Changed the way extra newlines are removed. Instead of removing extra
  newline characters, add a newline if one is not present. This is a bit
  cleaner.
- Note: I looked into using KERN_CONT to match the printk behavior to
  vsnprintf but this could cause issues with KTAP printing on the same line
  as interrupting kernel messages. I also looked at just adding KERN_CONT
  functionality to kunit_log and I did get this to work but it was a bit
  messy because it required a few calls to kunit_log_newline in
  kunit_run_tests. If this is very desired functionality, happy to add this
  to version 3.

 include/kunit/test.h   |  2 +-
 lib/kunit/kunit-test.c | 35 +++++++++++++++++++++++------------
 lib/kunit/test.c       | 18 ++++++++++++++++++
 3 files changed, 42 insertions(+), 13 deletions(-)

On Thu, 9 Mar 2023 at 04:40, Rae Moar <rmoar@google.com> wrote:
>
> Fix bug of the extra newline characters in debugfs logs. When a
> line is added to debugfs with a newline character at the end,
> an extra line appears in the debugfs log.
>
> This is due to a discrepancy between how the lines are printed and how they
> are added to the logs. Remove this discrepancy by checking if a newline
> character is present before adding a newline character. This should closely
> match the printk behavior.
>
> Add kunit_log_newline_test to provide test coverage for this issue.  (Also,
> move kunit_log_test above suite definition to remove the unnecessary
> declaration prior to the suite definition)
>
> As an example, say we add these two lines to the log:
>
> kunit_log(..., "KTAP version 1\n");
> kunit_log(..., "1..1");
>
> The debugfs log before this fix:
>
>  KTAP version 1
>
>  1..1
>
> The debugfs log after this fix:
>
>  KTAP version 1
>  1..1
>
> Signed-off-by: Rae Moar <rmoar@google.com>
> Reviewed-by: David Gow <davidgow@google.com>
> ---
>
> Changes from v3 -> v4:
> - Slight formatting change in test.h regarding "\" placement.
>

Thanks. This series looks good-to-go to me now!

Cheers,
-- David

> Changes from v2 -> v3:
> - Changes to commit message.
>
> Changes from v1 -> v2:
> - Changed the way extra newlines are removed. Instead of removing extra
>   newline characters, add a newline if one is not present. This is a bit
>   cleaner.
> - Note: I looked into using KERN_CONT to match the printk behavior to
>   vsnprintf but this could cause issues with KTAP printing on the same line
>   as interrupting kernel messages. I also looked at just adding KERN_CONT
>   functionality to kunit_log and I did get this to work but it was a bit
>   messy because it required a few calls to kunit_log_newline in
>   kunit_run_tests. If this is very desired functionality, happy to add this
>   to version 3.
>
>  include/kunit/test.h   |  2 +-
>  lib/kunit/kunit-test.c | 35 +++++++++++++++++++++++------------
>  lib/kunit/test.c       | 18 ++++++++++++++++++
>  3 files changed, 42 insertions(+), 13 deletions(-)
>
> diff --git a/include/kunit/test.h b/include/kunit/test.h
> index 0668d29f3453..9721584027d8 100644
> --- a/include/kunit/test.h
> +++ b/include/kunit/test.h
> @@ -420,7 +420,7 @@ void __printf(2, 3) kunit_log_append(char *log, const char *fmt, ...);
>  #define kunit_log(lvl, test_or_suite, fmt, ...)                                \
>         do {                                                            \
>                 printk(lvl fmt, ##__VA_ARGS__);                         \
> -               kunit_log_append((test_or_suite)->log,  fmt "\n",       \
> +               kunit_log_append((test_or_suite)->log,  fmt,            \
>                                  ##__VA_ARGS__);                        \
>         } while (0)
>
> diff --git a/lib/kunit/kunit-test.c b/lib/kunit/kunit-test.c
> index 4df0335d0d06..b63595d3e241 100644
> --- a/lib/kunit/kunit-test.c
> +++ b/lib/kunit/kunit-test.c
> @@ -443,18 +443,6 @@ static struct kunit_suite kunit_resource_test_suite = {
>         .test_cases = kunit_resource_test_cases,
>  };
>
> -static void kunit_log_test(struct kunit *test);
> -
> -static struct kunit_case kunit_log_test_cases[] = {
> -       KUNIT_CASE(kunit_log_test),
> -       {}
> -};
> -
> -static struct kunit_suite kunit_log_test_suite = {
> -       .name = "kunit-log-test",
> -       .test_cases = kunit_log_test_cases,
> -};
> -
>  static void kunit_log_test(struct kunit *test)
>  {
>         struct kunit_suite suite;
> @@ -481,6 +469,29 @@ static void kunit_log_test(struct kunit *test)
>  #endif
>  }
>
> +static void kunit_log_newline_test(struct kunit *test)
> +{
> +       kunit_info(test, "Add newline\n");
> +       if (test->log) {
> +               KUNIT_ASSERT_NOT_NULL_MSG(test, strstr(test->log, "Add newline\n"),
> +                       "Missing log line, full log:\n%s", test->log);
> +               KUNIT_EXPECT_NULL(test, strstr(test->log, "Add newline\n\n"));
> +       } else {
> +               kunit_skip(test, "only useful when debugfs is enabled");
> +       }
> +}
> +
> +static struct kunit_case kunit_log_test_cases[] = {
> +       KUNIT_CASE(kunit_log_test),
> +       KUNIT_CASE(kunit_log_newline_test),
> +       {}
> +};
> +
> +static struct kunit_suite kunit_log_test_suite = {
> +       .name = "kunit-log-test",
> +       .test_cases = kunit_log_test_cases,
> +};
> +
>  static void kunit_status_set_failure_test(struct kunit *test)
>  {
>         struct kunit fake;
> diff --git a/lib/kunit/test.c b/lib/kunit/test.c
> index 811fcc376d2f..e2910b261112 100644
> --- a/lib/kunit/test.c
> +++ b/lib/kunit/test.c
> @@ -108,6 +108,22 @@ static void kunit_print_test_stats(struct kunit *test,
>                   stats.total);
>  }
>
> +/**
> + * kunit_log_newline() - Add newline to the end of log if one is not
> + * already present.
> + * @log: The log to add the newline to.
> + */
> +static void kunit_log_newline(char *log)
> +{
> +       int log_len, len_left;
> +
> +       log_len = strlen(log);
> +       len_left = KUNIT_LOG_SIZE - log_len - 1;
> +
> +       if (log_len > 0 && log[log_len - 1] != '\n')
> +               strncat(log, "\n", len_left);
> +}
> +
>  /*
>   * Append formatted message to log, size of which is limited to
>   * KUNIT_LOG_SIZE bytes (including null terminating byte).
> @@ -135,6 +151,8 @@ void kunit_log_append(char *log, const char *fmt, ...)
>         vsnprintf(log + log_len, min(len, len_left), fmt, args);
>         va_end(args);
>
> +       /* Add newline to end of log if not already present. */
> +       kunit_log_newline(log);
>  }
>  EXPORT_SYMBOL_GPL(kunit_log_append);
>
> --
> 2.40.0.rc0.216.gc4246ad0f0-goog
>